1. Field of the Invention
The present invention relates to a method for forming a pattern such as wooden grain and the like on a surface of a synthetic wood board which is made of cellulose crushed material and thermoplastic resin material.
The synthetic wood board comprises wood meal obtained by pulverizing wood such as discarded constructional material or discarded materials of other products, or cellulose crushed material such as chaff, bagasse, crushed chip material or pulpwood. A large quantity of such synthetic wood boards are widely used for automobiles, appliances, living supplies and the like. The synthetic wood board is obtained by mixing thermoplastic resin materials which was obtained from a large number of discarded various thermoplastic resin waste materials with the above mentioned cellulose crushed material, and heating, kneading and molding the same. Therefore, the synthetic wood boards are extremely effective recycle products which reuse various discarded products. Heretofore, attempts have been made to develop molded resin products based on cellulose crushed materials such as wood meal of the above mentioned type, so as to improve resistance to water or heat, and the like. Such development of this kind of synthetic wood board have been made in view of securement of timber resource by requirement of environmental protection of earth, and in view of increase of timber cost, and visual deep latency requirement with respect to wood products. Further, developments have been demanded to enhance the value for the utilization of the synthetic wood boards as recycle products, by forming a deep wooden grain which is peculiarity of natural wood so as to provide a woody like appearance. Such wooden grain should have a surface in which the refractive index varies complicatedly, caused by the wood meal which is exposed to a surface on the synthetic wood board and where, light is irregularly reflected and will not be directly reflected. The present invention relates to the pattern forming method of the synthetic wood board according to such requirement.
The present invention is suitable for all usage of timber. The pattern formed by the invention can be used on decorative panel, wall material which had conventionally formed as plastic products, floor material, various decorative compound flooring boards, blocks, decorative floor boards, decorative boards made of natural wood, faced hard boards, or frame works having thickness of 30 mm or more as inner or outer decorative products for furniture, construction material, automobiles vehicles, and ships.
2. Description of the Prior Art
The synthetic wood board had conventionally been formed by mixing cellulose crushed material and thermoplastic resin, and kneading the same by extrusion process and molded into plate like shape. Such synthetic wood board had woody like appearance because it used cellulose crushed material as the main molding material. But there was still a need for approaching natural wood. Therefore, the resin skin layer on the surface of the synthetic wood board was removed by sanding, so as to provide a woody like appearance of cellulose crushed material more effectively.
However, the conventional synthetic wood board did not have a wooden grain and thus, woody like appearance of natural wood could not be obtained.
By printing such wooden grain on the surface of the conventional synthetic wood board, it was possible to make it look closer to a surface of natural wood. However, the resulting wooden grain pattern was monotonic and not deep, and thus was far from the appearance of natural wood.
The present invention has been accomplished to solve the above problems, and the object of the invention is to provide a pattern forming method of a synthetic wood board by forming, on a surface of the synthetic wood board, a pattern such as wooden grain which is close to the natural wood so as to improve its woody like appearance. More particularly, the object of the invention is to provide a method in which, by mixing cellulose crushed material and thermoplastic resin material of the synthetic wood board at an appropriate mixing ratio a woody like appearance of the synthetic wood board can be obtained, and by heating and kneading the resulting material to extrude the same into a molding die by a screw to mold the synthetic wood board, and forming a pattern such as a wooden grain in which the refractive index varies complicated by the wood meal which is exposed to a surface on the synthetic wood board, and light is irregularly reflected and will not be directly reflected.